STM32F4DISCOVERY - PC0 and PB2 pins

guitest02 · ‎2012-08-08

Posted on August 08, 2012 at 21:30

Hi,

I would like to have some more information in regard of the PC0 pin on the STM32F4Discovery. I read on the forum that quite some people use this pin as an adc channel, but on the User Manual I can see that it's already used by the development board for the USB PowerOn and I can see on the USB_OTG_FS schematic that it's used for USB_OTG_PowerSwitchOn.

So I'm wondering, is it just a feature like to activate a wakeup or something like that or it's necessary for the USB to work ? Can someone give a little explanation on this PowerSwitchOn and what it's used for ? If I remember well, I've seen someone using it at the same time as a virtual com port with the usb. So that's why I'm intrigued...

Another question, what is the PB2 pin used for ? is it just a pin that is not connected to the microcontroller ? Just wondering since there is nothing written on the manual but it's listed as a free I/O and it's not written ''nc'' on it.

Thanks a lot !

P.S. Sorry if it's a beginner question, I'm learning to work with microcontroller at the moment and have quite a big project in mind that I'll need to use many adc channels.

#stm32f4 #stm32f4discovery #pins

Tesla DeLorean · ‎2012-08-08

Posted on August 08, 2012 at 21:51

Doesn't PC0 allow you to apply 5V to the USB bus when you're a ''HOST'', ie powering an external USB peripheral? And that would presumably allow you to emulate a plug-in event to the attached peripheral.

PB2 is the BOOT1 pin, ie controls how the part starts at reset along with BOOT0, it's exposed on the connection, suggest you use as an output.

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raptorhal2 · ‎2012-08-08

Posted on August 09, 2012 at 01:21

....have quite a big project in mind that I'll need to use many adc channels.

While the F4 chip provides 16 or 24 external ADC channels, depending on package pin count, the F4 Discovery has 9 channels freely available, since some pins are wired to other functions. Learn as much as you can using the Discovery board before committing to making your own board.

Cheers, Hal

guitest02 · ‎2012-08-13

Posted on August 14, 2012 at 02:08

Thanks for your answers ! Special thanks to clive for all your contribution on this forum !! I learned a lot for your posts!

baird, for sure I'll try to learn as much as I can with the Discovery, I said that I need many adc channels... but that is subjectif, I'm sure a lot of people use more channels than I'll use. I plan on using about 12-13 channels and from what I can see, I'm able to have that amount of channels on the discovery if I don't use the MEMS mic and dac. So I'm sure I'll get some good time with the discovery !! Well, it's great to learn how to program it for now ! :)